Authorities are still searching the grounds and the house of Russell Dermond, the 88-year-old man who was found decapitated last week in Oconee, Ga., in an effort to discover clues concerning the grisly murder and, more importantly, the current whereabouts of his wife, Shirley, who police believe might have been abducted at the time of the killing. Putnam County sheriff Howard Sills said Monday that investigators were still at the Dermonds' home, dusting for fingerprints and interviewing people.

Investigators, faced with a lack of evidence, are finding it difficult to develop a motive. Sheriff Sills noted that the family did not appear to have criminal ties, nor was there reason to believe the decapitation was connected somehow to organized crime.

Russell Dermond's body was found beheaded by neighbors on Reynolds Plantation inside his million-dollar home on May 8. Since then, Sills said that the Putnam County Sheriff's Office has received about 20 calls per day.

But "no one" has called with a tip as to where Shirley Dermond might be, the sheriff said. Roughly 100 digital billboards lit up across Georgia with the 87-year-old woman's image.

In the last few days, Lake Oconee has been dragged. A Department of Natural Resources submarine robot was used Tuesday to search a particularly deep area in the lake near Reynolds Plantation. Searches have been conducted in the surrounding woods. Nothing was found.

Shirley Dermond seems to have vanished...

Authorities believe the murder and abduction occurred the weekend prior to the body being found. The home showed no signs of forced entry. Nothing of value seemed to be missing. The woman's purse, cell phone, and car keys were found at the scene.

“Quite candidly, this is the most baffling case we’ve ever worked,” the sheriff said at a press conference the day Russell Dermond's headless body was discovered. The severed head has yet to be found.